Flutter damper with air bleed



OC- 8, 1957 B. E. o'coNNoR ET A1. 2,808,904

rFLUTTER DAMPER WITH AIR BLEED 2 sheets-sheet 1 Filed Aug. 18, 1954 E QW @lv @SNS www@ N w whwl v'Eerfnfzm, E; .O'Cqfzwr -acfzmf E. Helma@ Oct. 8, 1957 B. E. o'coNNoR ETAL 2,808,904

FLUTTER DAMPER WITH AIR BLEED Filed Aug. 18, 1954 2 Sheets-Sheet 2 Bernard E'. 052122202" Raid fd' E. HEMGI FLUTTER DAMPER WITH AIR BLEED Bernard E. OConnor, Lake View, N. Y., and Richard E.

Henrich, Detroit, Mich., assignors to Hondaille Industries, Inc., a corporation of Michigan Application August 18, 1954, Serial No. 450,609

2 Claims. (Cl. 18S- 96) The present invention relates to improvements in flutter dampers for aircraft, and more particularly relates to dampers for eliminating utter of pivotally adjustable stabilizer and airfoil attachments such as elevators, ailerons, wing aps, and the like.

An important object of the present invention is to provide a hydraulic flutter damper structure operated by a linear piston movement rather than a rotary movement. v

Another object of the invention is to provide a flutter damper operated by a linear piston action and having means-for avoiding surges in the replenishing chamber due to variable piston rod displacements.

A further object of the present invention is to provide novel and improved replenishing and air bleeding systems for a utter damper.

Still another object of the invention is to provide novel and improved means for applying pressure to fluid in the replenishing chamber of a'utter damper.

A still further object of the invention is to provide an improved llutter damper that is low in cost, simple to install and service, and dependable and reliable in operation.

Other objects, features and advantages of the present invention will be readily apparent from the following detailed description of a preferred embodiment thereof taken in conjunction with the accompanying drawings, in which:

Figure l is a fragmentary side elevational view of a vibration damper embodying features of the present invention and showing the same associated with mounting brackets and attached to relatively movable parts of an aircraft wing structure, shown more or less schematically with certain parts of the wing broken away and in section;

Figure 2 is a vertical longitudinal sectional view through eter casing or housingmember `17 (Figures l and 2f), ex`VA tending across the joint between a movable control surface member 18`and anairplane airfoil assembly such as an elevator or 'wing 19. As is well known, the control"sur face member 18, whichin a stabilizer assembly comprises an elevator, and-in a wing assembly comprises an aileron, ap, or the like, ismounted to swing pivotally about an axis usually parallel to the edge of the airfoil b odymernber 19, and for this purpose, is provided with hinges (not shown) housed within the joint structure between the body and the movable control member.

Vthe'piston 30 by means of a screw 63".

2,803,994 Patented Oct. 8, 1957 The elongated housing member 17 of the utter damper is mounted between a lever 20 pivotal with the control member 18, for example about the axis of rotation of the control member, and a suitable bracket or the like indicated at 21 having a vertical pin 21 and secured with the airfoil body member 19. The casing or housing 17 is provided at its upper and forward end with a bracket 22 pivotal on a shaft 23 relative to the housing member 17 and having a vertical aperture 22a, Figure 2, receiving the vertical pin 21. The bracket 22 is iixed relative to the pin 21 for securing the housing 17 against displacement while accommodating rocking movement of the housing in a vertical plane about the shaft 23. At its lower and rearward end, the utter damper has a vbracket 25 pivotally mounted by vmeans of a shaft 26 and receiving the lever 20 by means of a vertical aperture 25a, Figure 2. Thus as the control member 18 tends to vibrate about its axis relative to the body member 19, the lever 20 will tend to axially shorten or elongate the utter damper which axial reciprocal movement is resisted by the mechanism to be hereinafter described.

For transmitting the relative movement of the lever 20 to the damper, the damper is provided with a rearwardly and downwardly extending piston rod or stem 30 providing attachment ears 31 receiving the shaft 26. At the interior of the housing member 17, the piston rod 30 is connected with a piston member 33 which cooperateswith the housing in defining a pair of working chambers 35 and 36; Axial vibration of the piston rod 30 and piston 33 is resistedby hydraulic fluid within theworking chambers. Displacement of the piston 33 is accommodatedV by liow ofv hydraulic iluid between the working chambers, permitting relatively free intentional movements of the control structure; however, Vthe flow of tluid is controlled in such` a way as to resist sudden or rapid movements of the control structure. The piston 33 is of size to form a relatively loose fit with the interior wall of housing 17 so as to avoid undue friction therewith and to avoid locking of the piston due to expansion thereof under high temperature working conditions. 1

f For dening a lixed wall of the working chamber 36, aplug 40 is threaded into the open lower end housing 17 and abuts against a shoulder 41 provided by the housing. The piston 30 reciprocates in van axial bore of the plug 4t), with an O-ring 43 being provided to seal the working chamber 36. The opposite fixed wall of the working chamber 35 is provided by an internal ange 45 integral with the casing 17. Y

For affording ow communication Ybetween the working chambers 35 and 36 in operation of the damper, displacement ports 5t) extend angularly through the piston member 33 from the working chamber 35 wto an interior annular-distribution channel 51 provided in the interior periphery of the piston 33. The piston rod 30l has a reduced end portion 54 extending piston 33 and provided with a radially extending passage 55 communicating` with channel 51. A sleeve'57 lits into the open end of the pistonreduced end portion 54 and abuts against an internal shoulder 58 of thepiston rodv30. vThis sleeve 57 has a port 60 registering with the passage-55 and communicating with the-interior space 62 of the sleeve 57. The sleeve is secured in placein A valve pl'g'65 is rotatably disposed withinthe sleeve 57 and has an' in` te'rior passage opening into the space 62 provided by the sleeve for communication with the ports 55 and 60. ,The interiorchamber of the plug 65Vis intersected atone side thereof by a relatively wide peripheral slot registering with a metering slit 71 in the sleeve 57. The metering slit 71V communicates with the working chamber .36, through aport 74 extending `throughthe piston' rod3tl.v`

of the v centrally through the asosoa By turning the valve member 65, it will be appreciated that the area of the metering slit 70 can be restricted by increments to increase the resistance to displacement of hydraulic fluid between the working chambersf,'as desired. There is thus provided avariableV displacement control orifice. Y

Means for effecting adjustments of the oriiice valve 65 comprise a stem 81 projecting axially through an axial bore 83 in the piston rod 30. At its outer end, the stem 81 is exposed Within an outwardly opening counterbored recess in the outer extremity of the piston rod 39. For turning the stem 81, a transverse handle pinvr 86 is provided which may also serve as an index pointer; Any adjusted condition of the valve is maintained by means of a lockV nut'37- which fis threaded 'onto the outer extremity portion ot 'the stem 815 andfin locked condition drives the pointer 86 clampingly` against bearing journal 99V for the stem. AfterA the desired adjustment has been eiected'and'the locknut`87 screwed down tight, avpositive closure cap 91 lis threaded into thel recess in the end ofthe pistonr'od 30. The bracket portion 31v may be welded to the end of the piston rodi-3i) as indicatedY at 95. In order to compensate for the great variation in .temperature encountered in the serviceof-the Hutter damper in an airplane, automatic thermostaticadjustment means are provided to effect compensations in the adjustment of the orifice valve 65 For this purpose a spiral thermostatic element 916 is connected between the valve mem. ber 65 andthe stem A81. so thatiwhile the stem 8-1is secured.. in xed 'primary adjusted condition, the thermostatic element `96.will1operate to close the oriiice from a meantemperature rated adjustmentwhen the temperature increases andthereby the viscosityof the uidislowered, and-to open the iiuid displacement oriiice when the temperature decreases below the mean rated adjustment and the .viscosity ofthe fluid increases. t

' Eorrnaintainingthe piston rod'displacement constant, apiston extension:'member1.0 0offthe` same exterior diame'ter as the` piston .rodllis threadedly engaged with the reducedend portion.5.4of therpiston rod to extend from the opposite endV of the piston member 33 .and thus. to displace anamount of liquid in theworking chamber` 35 equal to the volumeof liquid displaced-in the work-J ing chamber 361 .by the piston rod 3i).v Thus the piston rod displacement is not fafunction of pistonposition;

and'tconsequently. during operation there .isnoA surge. in. threplenishing chamber. (to befhereinafter. described) due, to variable piston rod displacement. The piston rod extension 10,0, is guided by. means of .a sleevellll which has an enlargedend, p ortionl 192 fitting within the .internal flange 45 of the housing andealed.theretobymeana of O. ring 1951.1 The, pistc'rtextension 1001's .sealed relative tothesleeve 101 b'y. means 'of an 0. ring 105. It will thusbeseen that the pistonmember 33 is supported in the. Casing by means of the piston. rod30` and piston rod extensionjl which, are slidably guided by'means ofthe plugAt) and sleeve 101, respectively, so that thereA is no; tendency .forthevpiston member 33, torest on the;

lowerfsurface of the jcaS ing,17; Frictional forces be-,

v i tween thlefpistonmember 3 3 and theV interior surface ofA the casing 1,7, aregthus distributed around theentire per ripheryvorf '-/the'pisptonhmember-- lt will be'observed inl Figure 2 that kbracket,.portion 196, mounting the brackety meansflZgZby means o f theshaft23 is clampedt-o. the end.

of'th Ncasi ng17 by means of a can 10j and that the sleeve,

the flange 45 and a secondary movable pistonV 111 slidable in an upper cylindrical end portion 113 of the 'casing 17. The replenishing chamber 110 communicates with the working chamber 35 by means of a replenishing passage 115 extending through the flange 45 and controlled against escape of hydraulic fluid'from the working cham ber 35 by means of a ball check valve 116. For supplying replenishing uid to the remote working chamber 36, a fittingl 118, Figure 3, extends into communication with the replenishing chamber 110 closely adjacent the` ange 45 in the manner indicated in Figure4 for the air bleeder tting to be hereinafter described. A fluid duct 119 connectsV the tting 11S with a fitting 120 connectingwith the lower remote end of the casingA 121 As indicated in Figure 2, the fitting 126 is threadedly engaged with the plug #i0 at the lower end of the casing and communicates with the remote working chamber 3 6 by means of a passage 122 under the control of a check valve 123.

Similarly, air bleeder passages communicate with the replenishing chamber from the upper portions ofthe respective working chambers, a direct passage through the flange 45 being indicated at 11Sg for bleeding air from the Working chamber 35 with means indicated at 117 preventing leakage of uid. The element 11T in Figure 2 threads into the enlarged end of `the passage 115' t0 substantially prevent ow ofv liquidwhile accommodating a bleed off of :air tothe passage 11S', the air leaking along a groove at the top of the Venlarged end of pas` sage 115' and about the rear margin of the element 117. For bleeding air from Athe` remotey working chamberf36, a very small passage indicated at- 12% extends around the plug 40 from the chamber 36 and axially to-a radial passage 121 in the plug@V whichinturn communicates with an Yaxial-bore 124 connecting with-a fittingy 125 having tubing 126- connecting with'I a fitting 12.7 opening into the replenishingchamber as indicated inv Figure 4 by means oa passage 113 between V the edge of the flange #i5-and` the adjacent` wallV of the. itt-ing- 127.` A closure plug or cap 139 is provided at the upper part of the casing 17 for. communication with the replenishing chamber 110wat the top thereof to bleed oft` any air which may accumulate in the replenishing chamber.

For providing asuitable. pressure in the `replenishment chamber 11i), the piston 111 is urged toward thema/all portioni by means of-a pair of springs 143 and 144 which are :disposed'in'tne `chamber in surrounding relation to Vthe sleeve 161. The. springs are bottomed against a peripheral `flange 1450i the bracket means 1%. An aperture 149. is provided in .thetwall of the. casing portion 113 and iscovered by a .closure .pl-ate. member 152. Removal of the closure plate 152 exposes a sleeve 154 which is,. connected withlthe. pist'on-11`1.l TheV sleeve .154y preti' erably has suitable gauge markings.longitudinally.spaced therealong which are visiblethroughtheaperture149 when the closure plate member is removed; The .gauge markings thus serve to indicate. the. locationl othe vpiston 111 so.thatthe condition of the replenishing. chamber.

can be ascertained by reference thereto. Suitable O.. rings 151 and 158 areprovided on the interionand exterior peripheryof the piston, member 111th. prevent leakage from lthe reolenishing, chamber 110.

. As indicated in Figure 3, a replenishment tvalve 160. is`

provided for accommodating jrefill of .the replenishment 10,1isthreaded, Vonto a portion '1.03ct thebracket 106 IQ;

conte; thevsleeve 1&1 axilallyof the casingrl?. Y It. is extrernelyh important forV eicient functioning ot theliutter damperL that the workingchambers 35'and12'i6-j n lat, all tim-esY thoroughly iillednwithbydraulio uid.; 4 dinglyfmeansfare-providedfor maintaining the` working chambers continuously, -supplied-with hydraulic. ugid 'under' areplenlishing pressure head ToV this end, the;v casingf17 isA .provided afrits upper forward ,f end withaly pressurized replenishing leliain ber'i'11i) dened between chamber as required.. The valveisplacedgin-a bore: 1t1`whichv communicatesy by means of apassage'f1621with; the replenishing chamber.IThe valve comprises a .valve bodyAportion 164 .having apassage` lficontrolled bymeans 0i a resilientcheck valvelblock: 165 whichis;re. siliently urged Vby means ot a spr-ing (notgshown) seated; against the. Spider 167 and urgingtheblock ll intra Sleting'relatim; TQ ill .the rerlenshiagfchambert, the plugk Vfis removedfrornlthebore 161 aloug,with itsl sealing ring 1771 and oil'underzpressureis forcedV intofthe.

' passage 168'and past, thejbloclg 165..againstfthefaction of, 75 i. Y

the spring. Y

The operation of the damper will be readily understood from the foregoing description. As the control member 18 in Figure 1 tends to vibrate about its pivot axis relative to the body 19, a resultant oscillation of the lever 20 is resisted by means of the damper construction 15. Specifically, if there is a vibrational force tending to suddenly move the piston rod 30 to the left as seen in Figure 2, the hydraulic fluid in the working chamber 35 resists such movement, while sudden movement to the right is resisted by the fluid in the working chamber 36 acting against the piston 33. Normal intentional adjustments of the control member 18 relative to the body 19 are accommodated by the metered flow of fluid, for example, from the working chamber 35 to chamber 36 through the passage 50, ports 55 and 60, to chamber 62 and from the chamber 62 out through the metering slit 71 and the port 74 under the control of the valve plug 65. The replenishing chamber 110 is operative to feed fiuid to the working chamber 35 through the check valve passage 115 and to the working chamber 36 through the tubing 119 and fitting 120 at the remote end of the casing through check valve passage 122. Any a-ir in the working chambers will be forced through the bleed passage 115 for working chamber 35, and through bleed passages 120', 121 and 124 to the tubing 126 and into the replenishing chamber 110 through the passage 128 indicated in Figure 4 for chamber 36.

During filling of the unit with hydraulic fluid, the air bleed plug 130 is loosened so that air can escape from the interior of the unit. When the hydraulic fluid introduced through the valve 160, Figure 3, has filled the working chambers and shows at the air bleed vent, the plug 130 is tightened to seal the vent.

It will be understood that modifications and variations may be effected without departing from the scope of the novel concepts of the present invention.

We claim as our invention:

1. A hydraulic apparatus comprising a housing having an interior spa-ce, first and second wall members defining opposite ends of said space, a piston member reciprocal in said space and dividing the space into separate working chambers, a piston stem projecting into said housing through said first Wall member, a piston extension of exterior cross section substantially equal to the exterior cross section of said piston stern extending through said second wall member and connected to said piston member, a sleeve member extending from said second Wall member within said housing and receiving said piston eX- tension in sliding relation to the interior surface thereof, said sleeve member and said housing having an annular space therebetween, an annular piston member in said space and slidable on said sleeve member to provide a replenishing chamber between said annular piston member and said second wall member, compression spring means encircling said sleeve member and acting on said annular piston member to urge the same toward said second wall member, said second wall member having a replenishing duct affording communication between said replenishing chamber and the Working :chamber adjacent thereto, a oneway valve in said replenishing duct preventing flow of fluid from said adjacent working chamber to said replenishing chamber, and said wall member having an air bleed duct at the top thereof affording communication between said adjacent working chamber and said replenishing chamber to bleed air from said adjacent work chamber. 2. A hydraulic apparatus comprising a housing having an interior space, first and second wall members defining opposite ends of said space, a piston member reciprocal in said space and dividing the space into separate working chambers, a piston stem projecting into sai-d housing through said first wall member, a piston extensie-n of exterior cross section substantially equal to the exterior cross section of said piston stem extending through said second wall member and connected to said piston men1 ber, a sleeve member extending from said seco-nd wall member within said housing and receiving said piston extension in sliding relation to the interior surface thereof, said sleeve member and said housing having an annular space therebetween, an annular piston member in said space and slidable on said sleeve member to provide a replenishing `chamber between said annular piston member and said second wall member, compression spring means encircling said sleeve member and acting on said annular piston member to urge the same toward said second wall member, said second wall member having a replenishing duct affording communication between said replenishing chamber and the working chamber adjacent thereto, a oneway valve in said replenishing duct preventing flow of fluid from said adjacent working chamber to said replenishing chamber, and said wall member having an air bleed duct at the top thereof affording communication between said adjacent working chamber and said replenishing chamber to bleed air from said adjacent work chamber, said first wall member having a replenishing duct therein leading into the working chamber adjacent thereto, a pipe connecting said replenishing chamber with said replenishing duct in said first wall member, a one-way valve in said first wall member controlling flow of fiuid in said replenishing duct and preventing flow of fluid from the working chamber adjacent `said first wall member to said replenishing chamber, and a further pipe affording an air bleed connection between the working chamber adjacent said first wall member and said replenishing chamber.

References Cited in the file of this patent UNITED STATES PATENTS 1,072,350 Muller Sept. 2, 1913 1,434,197 Brown Oct. 31, 1922 1,825,233 Joyce Sept. 29, 1931 2,334,115 Meredith Nov. 9, 1943 2,342,381 Thornhill Feb. 22, 1944 2,410,176 Y Magrum Oct. 29, 1946 2,419,651 Magrum Apr. 29, 1947 2,664,255 Crandall et al Dec. 29, 1953 FOREIGN PATENTS 299,670 Great Britain Nov. 1, 1928 

